Stock-Based Compensation - Stock Options (Details) shares in Thousands	12 Months Ended
	May 31, 2017 $ / shares shares
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	2,334
Weighted-Average Remaining Contractual Life in Years	6 years 9 months 18 days
Weighted-Average Exercise Price (in dollars per Share)	$ 23.02
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	910
Weighted-Average Exercise Price (in dollar per Share)	$ 21.97
$12.00 - $20.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	12.00
Option Exercise Price Range, high end of range (in dollars per share)	$ 20.00
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	500
Weighted-Average Remaining Contractual Life in Years	4 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per Share)	$ 14.02
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	349
Weighted-Average Exercise Price (in dollar per Share)	$ 14.49
$20.01 - $26.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	20.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 26.00
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	1,305
Weighted-Average Remaining Contractual Life in Years	7 years 7 months 6 days
Weighted-Average Exercise Price (in dollars per Share)	$ 24.72
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	322
Weighted-Average Exercise Price (in dollar per Share)	$ 25.44
$26.01 - $34.50
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	26.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 34.50
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	529
Weighted-Average Remaining Contractual Life in Years	7 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per Share)	$ 27.36
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	239
Weighted-Average Exercise Price (in dollar per Share)	$ 28.25